mp2002-tut 1
TRANSCRIPT
MP2002 Kinematics and Dynamics of Machinery
Tutorial 2
2009/2010 Sem 2
1 Done by Deng Lixi: [email protected]
Pin-in-slot joint
TUTORIAL 1
MP2002 Kinematics and Dynamics of Machinery 1.1 (Tutoiral) Identify the types of links and joints of the mechanism as shown below and determine its
degrees of freedom.
1.2 Sketch the kinematic disgrams of the planar mechanisms and find the mobility.
(c) (d)
1.3 (Homework) The figure below shows the line drawing of a commercially available exercise machine.
(a) Exaplain why the machine can be treated as a planar mechainsm when performing motion analysis.
MP2002 Kinematics and Dynamics of Machinery
Tutorial 2
2009/2010 Sem 2
2 Done by Deng Lixi: [email protected]
(b) Sketch the kinematic drawing of the exercise machine and determine its degrees of freedom.
(c) If the pin joint at B is moved to the alternate connection B’, will this make the workout harder or easier ?
1.4 (Wilson & Sadler, Q1.18 & 1.20, p.91) (Tutoiral) For the following two cases :
(a) L0 = 4, L1 = 1, L2 = 2, L3 = 1.5
(b) L0 = 2.5, L1 = 1, L2 = 2.5, L3 = 2
(i) determine whether the links can actually form a mechanism with the dimensions given;
(ii) if a mechanism exists, identify the type of mechanism (crank rocker, drag link, double-rocker, triple-rocker,
change-point).
Additional Questions
1.5 (Wilson & Sadler, Q1.24, p.91) Given L1 = 100 mm, L2 = 280 mm and L3 = 360 mm, find the range of
values for the unknown link L0 if the linkage will theoretically act as a :
(a) crank rocker mechanism; (b) drag link mechanism; (c) double-rocker mechanism;
(d) change-point mechanism; (e) Grashof mechanism; (f) triple-rocker mechanism.
1.6 The Figure below shows the folding mechanism of a camera in its opened position.
Sketch the kinematic diagram of the folding mechanism and determine its degrees of freedom.
MP2002 Kinematics and Dynamics of Machinery
Tutorial 2
2009/2010 Sem 2
3 Done by Deng Lixi: [email protected]
Solutions:
1.1 Hint: DOF=3*(nl-1)-2*n’j-n’’j
Solution:
nl=5,
n’j=5,
n’’j=1
DOF=3*(5-1)-2*5=1
1.2 Hint: DOF=3*(nl-1)-2*n’j-n’’j
Solution:
(a)
DOF=3*(9-1)-2*10=4
(b)
DOF=3*(7-1)-2*7=1
MP2002 Kinematics and Dynamics of Machinery
Tutorial 2
2009/2010 Sem 2
4 Done by Deng Lixi: [email protected]
(c)
DOF=3*(7-1)-2*9=0
(d) DOF=3*9-2*3=1
1.3 Hint: DOF=3*(nl-1)-2*n’j-n’’j
Solution:
DOF=3*(4-1)-2*4=1
It will be easier. Because the crank is shorter, so ømin is larger, which means smaller force to input.
1.4 Hint: DOF=3*(nl-1)-2*n’j-n’’j
And please refer to notes about the definition about different definition of mechanisms.
Solution:
(a) Yes, it is a triple rocker
(b) Yes, it is a crank rocker
MP2002 Kinematics and Dynamics of Machinery
Tutorial 2
2009/2010 Sem 2
5 Done by Deng Lixi: [email protected]
1.5 Hint: DOF=3*(nl-1)-2*n’j-n’’j
And please refer to notes about the definition about different definition of mechanisms.
Solution:
(a) 180<L0<540
(b) 0<L0<20
(c) Think: As L2 is the minimum, please calculate yourself.
(d) 180 or 540
(e) 180<L0<540
(f) 20<L0<180 or L0>540
1.6 Hint: DOF=3*(nl-1)-2*n’j-n’’j
Solution:
DOF=3*(6-1)-2*7=1